PANCREATIC DIGESTION. 61 



PANCREATIC RENNIN. 



The ability of pancreatic juice to cause the clotting of 

 milk has long been known; but only of late has the action 

 been ascribed to a definite enzyme, which, on account of the 

 similarity in its function to the milk-clotting enzyme of the 

 stomach, has been called pancreatic rennin. This sub- 

 stance also possesses the power of bringing about a peculiar 

 changed condition of the caseinogen of the milk by which 

 the protein is rendered liable to coagulation. The coagu- 

 lable protein is termed metacasein, and its appearance is 

 denoted as the metacasein reaction. Metacasein is appar- 

 ently an intermediate stage in the action of the pancreatic 

 rennin upon caseinogen, in which pancreatic casein is the 

 end product. Pancreatic casein differs in some slight degree 

 from true casein. 



(a) To 5 c.c. of milk add 1 c.c. of the pancreatic extract 

 and place the mixture at 40 C. Note the formation of the 

 clot. 



(6) To 10 c.c. of the milk add 1 c.c. of the pancreatic ex- 

 tract diluted with 2 volumes of water. Place the test-tube 

 at 40 C. and from time to time remove portions (1 c.c.) of 

 the mixture and heat each to boiling. In one of them 

 coagulation in fine flakes will occur. Note the time from the 

 beginning of the experiment. 



(c) Make an exact duplicate of the preceding experi- 

 ment, and at the time at which the appearance of the meta- 

 casein reaction would be expected, judging from the last 

 experiment, take out the tube from the bath. Examine 

 a drop under the microscope. Stand the tube in a cool 

 place and note the formation of a clot. This will dissolve 

 when replaced in the water-bath. 



